U.S. patent number 5,389,425 [Application Number 07/777,317] was granted by the patent office on 1995-02-14 for packaging materials.
This patent grant is currently assigned to Courtaulds Packaging Limited. Invention is credited to Andrew Holloway, David N. Platt.
United States Patent |
5,389,425 |
Platt , et al. |
February 14, 1995 |
Packaging materials
Abstract
A water soluble, or water dispersible, polymeric film comprising
a layer of a first polymer resistant to dissolution and/or
softening on handling with wet hands, and a layer of a second
polymer resistant to insolubilization in water by perborate ions.
Such films have a variety of uses particularly when they have a
layer of an at least cold water soluble polymer between the layers
of the said first and second polymers, for example in the packaging
log washing products or agrochemicals. The first polymer layer is
preferably discontinuous so that in the large body of water the
film has reduced strength so that water can pass through the film
when the film is agitated in the water.
Inventors: |
Platt; David N. (Bridgwater,
GB2), Holloway; Andrew (Witney, GB2) |
Assignee: |
Courtaulds Packaging Limited
(Essex, GB)
|
Family
ID: |
10675291 |
Appl.
No.: |
07/777,317 |
Filed: |
December 3, 1991 |
PCT
Filed: |
May 01, 1991 |
PCT No.: |
PCT/GB91/00700 |
371
Date: |
December 03, 1991 |
102(e)
Date: |
December 03, 1991 |
PCT
Pub. No.: |
WO91/17202 |
PCT
Pub. Date: |
November 14, 1991 |
Foreign Application Priority Data
Current U.S.
Class: |
428/195.1;
428/507; 428/515; 428/913; 428/35.2 |
Current CPC
Class: |
C11D
17/042 (20130101); C08J 7/0427 (20200101); C08J
5/18 (20130101); Y10T 428/24802 (20150115); Y10T
428/3188 (20150401); Y10T 428/1334 (20150115); Y10S
428/913 (20130101); C08J 2329/04 (20130101); Y10T
428/31909 (20150401) |
Current International
Class: |
C11D
17/04 (20060101); C11D 1/00 (20060101); B65D
65/46 (20060101); C08J 5/18 (20060101); C08J
7/04 (20060101); C08J 7/00 (20060101); B32B
027/14 (); B32B 027/08 (); C11D 017/00 () |
Field of
Search: |
;428/905,195,507,515,913
;252/90 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
0011502 |
|
May 1980 |
|
EP |
|
0079712 |
|
May 1983 |
|
EP |
|
0217186 |
|
Apr 1987 |
|
EP |
|
2083762 |
|
Mar 1982 |
|
GB |
|
2109706 |
|
Jun 1983 |
|
GB |
|
Primary Examiner: Lesmes; George F.
Assistant Examiner: Shelborne; Kathryne E.
Attorney, Agent or Firm: Bacon & Thomas
Claims
We claim:
1. A water soluble or water dispersible polymeric film comprising a
first discontinuous layer of a polymer resistant to dissolution
and/or softening on handling with wet hands and selected from
nitrocellulose or polyvinylidene chloride; a second layer made from
a heat sealable polymer which is water soluble and resistant to
insolubilization in water by perborate ions and selected from a
polyvinyl alcohol or an acrylic; and an intermediate layer
interposed between said first and second layers, said intermediate
layer being a cold water soluble polyvinyl alcohol which is
resistant to insolubilization by perborate ions.
2. A water soluble or water dispersible polymeric film comprising a
first layer of a polyvinyl alcohol having a degree of hydrolysis of
about 90 to 99% resistant to dissolution and/or softening on
handling with wet hands; a second layer made from a heat sealable
polymer which is water soluble and resistant to insolubilization in
water by perborate ions and selected from a polyvinyl alcohol or
acrylic; and an intermediate layer interposed between said first
and second layers, said intermediate layer being a cold water
soluble polyvinyl alcohol having a degree of hydrolysis of about 75
to 80% which is resistant to insolubilization by perborate
ions.
3. A film according to claim 1, wherein the said first polymer
layer comprises nitrocellulose.
4. A film according to claim 1 wherein the said second layer
comprises a water-soluble acrylate.
5. A container comprising a film according to claim 1.
6. A container according to claim 5, in the form of a sachet.
7. A container according to claim 5, wherein the film is heat
sealed.
Description
This invention concerns water soluble or water dispersible
packaging materials.
Water soluble and water dispersible packaging materials have been
proposed hitherto, in particular for packaging materials which are
themselves to be dissolved and/or dispersed in water. Thus it has
been proposed to package soaps or detergents in water soluble
polymeric films, for example polyvinyl alcohol films, or in paper
containers bonded by a water soluble adhesive. Hitherto proposed
polyvinyl alcohol films often have the disadvantage that they start
to dissolve when handled with wet hands. Furthermore, substances
present in the packaged materials can inhibit dissolution of the
polyvinyl alcohol and therefore defeat the object of having a
soluble film. Thus borate ion-containing materials tend to cause
gelling of polyvinyl alcohol which inhibits its dissolution. It has
been proposed in European Patent Specification 79712, for example,
to incorporate certain polyols such as sorbitol in the polyvinyl
alcohol to reduce this undesirable gelling effect, but it doesn't
address the problem of softening and/or partial dissolution on
handling. Dispersible paper containers suffer from the disadvantage
that the paper itself remains and has to be physically removed for
example from a load of washing in a washing machine. Such paper
containers have proved to be unacceptable to consumers.
An alternative approach to these problems described in GB 2109706A
is to make containers for such products from a base film of an at
least partially water-soluble plastics material carrying on one
surface a protective layer of particles of polytetrafluoroethylene,
the layer of particles preventing the packaged product from
contacting the water-soluble plastics material, for example of
polyvinyl alcohol. Such containers are complicated to produce as
areas of the film where heat seals are to be formed should not have
a layer of polytetrafluoroethylene thereon.
According to the present invention there is provided a water
soluble or water dispersible polymeric film comprising a layer of a
first polymer resistant to dissolution and/or softening on handling
with wet hands, and a layer of a second polymer resistant to
insolubilization in water by perborate ions.
Although films of the present invention can consist of the two
specified layers, it is generally preferred to incorporate a layer
of an at least cold water soluble polymer between the said first
and second layers. This has a number of advantages, for example the
choice of materials for the first and second layers is generally
wider when such a third layer is present, and these third layers
also often serve to impart improved mechanical properties to the
films.
The first polymer layer should be of a polymeric material which
imparts to the film resistance to dissolution and/or softening on
handling the film with wet hands. Preferred polymeric materials for
the purpose include nitrocellulose, polyvinylidene chloride and
polyvinyl alcohol having low solubility at ambient temperature,
when the polymeric materials such as nitrocellulose or
polyvinylidene chloride are used, they preferably form an
incoherent layer so that when it is intended to cause dissolution
or dispersion of the film in water, the water can reach the layer
or layers underneath. Such layers can be produced by known methods,
for example gravure printing.
Layers of polyvinyl alcohol used for the first layer should have
only low solubility at ambient temperature. The precise temperature
at which solubility occurs is generally not critical. However, it
is generally preferred that the polymer layer doesn't feel sticky
on normal handling, for example when a container of a washing
powder produced from a film of the present invention is placed in a
washing machine using wet hands. It is generally preferred that
this should be so for a period of about two minutes. The polyvinyl
alcohol should, however, be sufficiently soluble that the film will
dissolve and/or disperse at a desired elevated temperature at which
the contents of a container made of a film of the invention should
be released from the container. The polyvinyl alcohol used for the
first layer is preferably a hydrolysed polyvinyl acetate having a
degree of hydrolysis of from 80 to 99 percent, and especially from
90 to 99 percent.
The third layer, when present, is conveniently made of a cold water
soluble polymer, the first polymer layer serving to protect this
layer from dissolution for example when the film is handled.
Examples of polymers which can be used include polyvinyl alcohol,
methyl cellulose, poly-(ethylene oxide) and poly-(ethyloxazalene),
polyvinyl alcohol generally being preferred. Particularly preferred
polyvinyl alcohols are polyvinyl acetates having a degree of
hydrolysis of from 70 to 99 percent, and especially from 75 to 80
percent.
The layer of the first polymer will usually contain substances
which impart other properties to the films, for example antiblock
agents (e.g. silica with an average particle size up to 20
microns), surfactants, processing aids (e.g. calcium stearate,
stearic acid or polyvinyl acetate), solvents (e.g. water) or
plasticisers. The choice of such substances will, as will be
appreciated by those skilled in the art, depend upon the nature of
the first polymer itself, plasticisers for example usually being
used with polyvinyl alcohol. The plasticiser is preferably a
polyhydric alcohol, for example glycol, diglycol, triglycol,
sorbitol, manitol, a polyethylene glycol, dipropylene glycerol,
1,2-propane diol, 1,3-propane diol, 1,2-butane diol, 1,3-butane
diol, 1,4-butane diol, 1,5-pentone diol, 1,5-hexane diol,
1,6-hexane diol, 1,2,6-hexane triol, 1,3,5-hexane triol, neopentyl
glycol, trimethylol propane or a fatty acid monoglyceride. Water
can also be used as a plasticiser. When a third layer is present
consisting of polyvinyl alcohol or a vinyl alcohol copolymer, a
plasticiser is also preferably included in the layer. Examples of
plasticisers which can be used in the third layer include those
which can be used for the first layer.
The second polymer layer is preferably heat sealable, for example
to itself. This can enable films of the present invention to be
formed into containers using known methods. Preferred polymers for
the second layer which are heat sealable include polyvinyl alcohol
containing a plasticiser as described hereinbefore for the polymer
layer which is resistant to dissolution and/or softening, or a
water, soluble acrylic polymer. Heat sealing desirably occurs at a
temperature of less than 100.degree. C. It is also desirable that
the second polymer layer be stable at temperatures used to produce
films of the present invention, for example at temperatures of from
180.degree. to 200.degree. C. When a water soluble acrylic polymer
is used, it will in general be applied as a solution of the polymer
in a non-aqueous solvent. The solvent used will usually depend upon
the particular acrylic polymer concerned, iso-propanol,
tetrahydrofuran, toluene and methylethylketone being examples of
solvents which can be used to dissolve acrylic polymers. A
preferred group of acrylic polymers for use in accordance with the
present invention contains units derived from one or more of
acrylic esters, acrylic acid, acrylamide methacrylic esters and
methacrylic acid. It is generally preferred to avoid the use of
aqueous solutions of water soluble acrylic polymers since they
would tend to cause dissolution of the water soluble layers of the
films.
As will be appreciated, a variety of combinations of polymer layers
are envisaged within the scope of the present invention.
In one combination, a discontinuous layer of a water insoluble
polymer, for example nitrocellulose, is provided on a layer of
polymer resistant to gelling by perborate ions, for example
polyvinyl alcohol containing a plasticiser, e.g. sorbitol or
manitol. Films of this structure can be used for various purposes,
depending upon the temperature at which the polymer layer resistant
to gelling is soluble. Cold water solubility is desirable for
example for films of the invention which are to be used to package
wallpaper paste, agrochemicals, or cold water washing products.
Warm or hot water solubility is generally preferred when the films
are to be used to package materials which are themselves to be used
at elevated temperatures, e.g. washing products.
Alternatively, a two layer film in accordance with the present
invention can consist of a layer of cold water soluble polymer in
combination with a layer of a polymer having low solubility at
ambient temperature but being soluble at elevated temperatures. The
cold water soluble polymer is then preferably a polyvinyl alcohol
containing a substance which imparts resistance to insolubilization
by borate ions, for example a polyol plasticiser, e.g. sorbitol or
manitol. The polymer having low solubility at ambient temperature
but being soluble at elevated temperatures is also preferably of a
polyvinyl alcohol. Although this layer can include a substance
which imparts resistance to insolubilization by borate ions, for
example as described for the cold water soluble layer, this is
usually not required.
Preferred three layer structures for films of the present invention
include two layers similar to, or even identical to, those
hereinbefore described for films consisting of two layers. The
additional polymer layer should, however, provide the films with
resistance to insolubilization by borate ions. This can enable the
other layers of the films to be composed of polymers which are not
necessarily resistant to insolubilization by borate ions. The
preferred polymer for the additional polymer layer is of a water
soluble acrylic polymer, preferably as hereinbefore described.
A particularly preferred three layer film in accordance with the
present invention consists of a core layer of cold water soluble
polyvinyl alcohol with an incoherent layer of nitrocellulose on one
surface and a coherent layer of an acrylic polymer on its other
surface, the core layer preferably not including a polyol
plasticiser.
Films of the present invention can be produced by known methods.
Layers including polyvinyl alcohol are conveniently produced by
extrusion, and where more than one such layer is present, they can
conveniently be produced by coextrusion. Layers of other materials,
for example nitrocellulose, polyvinylidene chloride or an acrylic
polymer, are often conveniently formed from a lacquer using a
suitable solvent.
The thickness of the various layers of films of the present
invention can be varied according to the nature of the materials
forming those layers and the properties desired for the films.
Typically the films will be from 10 to 100 microns thick, with the
first polymer layer being from 2 to 9 microns thick and the second
polymer layer being from 3 to 6 microns thick. The third layer,
when present, will usually be from 10 to 100 microns thick and
preferably from 20 to 50 microns thick.
Films of the present invention can be used to package a variety of
materials, and especially materials which are themselves to be
dissolved in water. Films of the present invention will usually be
used in such a way that the layer having resistance to dissolution
and/or softening on handling with wet hands will provide the
surface which is handled. The other surface of the films will then
contact the packaged materials. Materials which can be packed using
films of the present invention can be solid or liquid, and examples
of materials which can with advantage be packaged using films of
the invention include wallpaper paste, washing powders and
agrochemicals. The present invention therefore in addition provides
packages of materials, the packages being made using a film of the
present invention. For example, packages of the present invention
can be in the form of sachets.
Packages including films of the present invention can be produced
using known methods. It is generally preferred to use the heat
sealable properties of the films themselves when they are in fact
heat sealable. It is, of course, also possible to use an adhesive
layer applied to the film where desired.
The following Examples are given by way of illustration only. All
parts are by weight unless indicated otherwise.
EXAMPLE 1
Using a high shear mixer, 60 parts of polyvinyl alcohol (degree of
hydrolysis 77 percent, viscosity 11 cps--a cold water soluble
grade) were mixed with 7.5 parts of dipropyleneglycol, 0.06 parts
of calcium stearate and 0.36 parts of silica having a particle size
of about 5 microns. The mixture was then extruded through an
annular die and blown using a blow up ratio of 2.5:1 to produce a
film 30 microns thick.
One surface of the resulting polyvinyl alcohol film was then coated
with a nitrocellulose lacquer using a forward gravure method on an
RK KOATER (Trade Mark) coating machine, the lacquer being heated to
50.degree. C. and agitated during the coating procedure to dissolve
the waxes in the lacquer. Coating was effected using a gravure
cylinder having a rectangular array of 150 depressions per 25.4 mm
in each direction, the depressions being 380 microns deep, and a
pressure of 10 psi. The coated film was heated to dry the lacquer,
after which it was wound up. The dried nitrocellulose coating was
discontinuous as a result of the Pattern on the gravure roller.
The other surface of the polyvinyl alcohol film was coated with a
cold water soluble acrylic coating composition using similar
conditions to those used to coat the fill with the nitrocellulose
lacquer, but the acrylic coating composition was applied by reverse
gravure coating. The acrylic coating composition was a solution of
an acrylic acid/acrylamide/methacrylic acid copolymer in a mixture
of tetrahydrofuran and iso-propanol (20:80). The dried acrylic
coating was continuous.
The resultant film was subjected to various tests, as follows:
(a) dissolution test A square sample of the film 5 cm.times.5 cm
was weighed, as was a 100 gauge mesh (150 micron pore size). The
sample of film was stirred for 3 minutes in 300-400 cc of water,
and the solution was filtered through the mesh. The mesh was
allowed to dry, and it was reweighed. The amount of undissolved
film calculated from the increase in weight of the mesh was 10
percent.
(b) perborate resistance test The acrylic coated surface of a
square sample of the above film 5 cm.times.5 cm but without the
nitrocellulose coating was covered with a washing powder containing
a perborate. The sample was left for four weeks and the dissolution
test described above was carried out. The amount of undissolved
film was 1.35 percent compared with 5.1 percent for a fill of the
polyvinyl alcohol without the acrylic or nitrocellulose
coatings.
(c) water drip through test A sample of the film was stretched over
a beaker with the nitrocellulose coated surface uppermost and a
droplet of water was placed on the surface of the film. The water
took two minutes to dissolve through the film, the time taken for
water to dissolve through a mono-layer of the polyvinyl alcohol
being about five seconds. This test indicated that the film of the
invention had resistance to softening on handling with wet hands.
This was confirmed in practice by the nitrocellulose surface of the
film of the invention not feeling sticky after two minutes whereas
a mono-layer of the polyvinyl alcohol of the core of this film
having softened and felt very sticky after this period.
EXAMPLE 2
A two layer polymeric film was produced by coextruding the
polyvinyl alcohol described in Example 1 with a layer of a similar
but hot water soluble grade of polyvinyl alcohol having a degree of
hydrolysis of 98 percent and a viscosity of 10 cps. The hot water
soluble layer was 9 microns thick and the cold water soluble layer
was 21 microns thick.
The cold water soluble surface of the film was then coated with the
acrylic composition as described in Example 1.
The amount of undissolved film in the dissolution test described in
Example 1 was 20 percent. In the water drip through test, the water
took fifteen minutes to dissolve through the film from the side
consisting of the hot water soluble polyvinyl alcohol. The hot
water soluble polyvinyl alcohol layer behaves similarly to the
nitrocellulose layer of the film of Example 1 when handled with wet
hands.
* * * * *